The present invention is in the field of systems that control pressure within enclosures and, more particularly, in the field of testing of pressure control systems which operate in vehicles such as aircraft.
In a typical modern aircraft, flights occur at high altitudes where atmospheric pressure is substantially lower than that which can be tolerated by aircraft passengers. Such aircraft employ a cabin-pressure control system that maintains a cabin pressure at tolerable levels irrespective of actual atmospheric pressure at the altitude in which the aircraft may be operating. Cabin-pressure control systems must have a capability of continuously modifying cabin pressure relative to atmospheric pressure. As the aircraft climbs after take-off, cabin pressure must progressively change from ground level pressure to a desired cabin pressure, e.g. a pressure that corresponds to an altitude of about 8000 ft above sea level. As the aircraft climbs above 8000 ft., relative cabin pressure (i.e. cabin pressure relative to external atmospheric pressure) must continuously increase. But, the actual internal pressure of the cabin must remain at the 8000 ft. pressure.
Conversely, as the aircraft descends for landing, the relative cabin pressure must continuously decrease to reduce the cabin altitude to the ground level pressure for when the aircraft lands. During this time, the absolute cabin pressure is increasing.
A cabin-pressure control must be constructed and tailored to operate correctly within a particular aircraft configuration. Aircraft configurations continually evolve. Consequently, cabin-pressure control systems must evolve correspondingly. Also, continuing effort is directed to improving the efficiency and accuracy of cabin-pressure controls systems. Both of these factors produce a need for evaluating the effectiveness of newly designed or newly modified cabin-pressure systems before they are actually incorporated into an operating aircraft.
In the prior art, such evaluation is performed in large altitude chambers. Such a chamber must be large enough to accommodate an aircraft cabin. The altitude chamber must be provided with a vacuum system that produces a reduced pressure at an exterior of the cabin to simulate high altitude flight. Altitude chambers are expensive to build and expensive to operate.
There is a long standing desire to be able to evaluate new designs and modification of cabin-pressure control systems with bench testing, i.e., without using altitude chambers. Computer modeling has been considered as an alternative to altitude chambers. Computer modeling has succeeded in producing preliminary evaluations, but final prior-art evaluations still require use of an altitude chamber.
Bench testing is made difficult by another factor. A full prior-art test of control system requires that it be attached to its associated outflow valves. In many types of aircraft, outflow valves are large structures that may be incorporated into a body of the aircraft. In some cases the outflow valves may be motor driven or driven by hydraulic or pneumatic actuators.
As can be seen, there is a need to provide a system for fully evaluating new designs and modifications of cabin-pressure control systems without use of an altitude chamber. Additionally there is a need to provide such a system that does not require attachment of outflow valves to the tested control system.